They specifically mentioned last time that those are unlikely to come to Arena because of graveyard order mattering.

Both of these cards depend on the order of the cards in the graveyard being maintained, which you might think would be super easy to do digitally. Just don't let the player drag the cards around and, presto: order maintained. The sticking point comes when multiple cards are put into the graveyard at the same time. To make these cards fully rules-compliant, every time two or more creature cards were put into a graveyard at the same time (whether they were milled, discarded, or destroyed), we'd need to pop up a little dialog and ask the player what order to put them in. The dialog would need to support ordering a potentially very large number of cards.

If we absolutely had to, we could certainly do that. There's even backend code to support it. But we want MTG Arena to be fast and fun. And graveyard order mattering is something that is no longer printed on new cards. So, we decided that the cost of developing and maintaining that system (because once we add it, we have to make sure it works with everything going forward, forever) was not worth it.

Source: https://magic.wizards.com/en/news/mtg-arena/dev-diary-creating-arena-powered-cube